VH45DET - 446wHP - 93 octane - 6psi

[Jeff Taylor]

You probably have the stock 270 cc/min injectors in that engine right now. You could easily swap in the stock injectors from a 300zx twin turbo, which are 370 cc/min. On these injectors, you should have enough fuel for 6psi of boost on most superchargers. These injectors should support between 275 - 300 wheel-HP safely.

If you ever foresee yourself wanting to run more boost, or make more power than 300wHP, then I would advise upgrading to a larger injector, such as a 550cc/min. For simplicity, you'll want to stick with side-feed injectors made for Nissan engine setups, because they will swap right in without needing to fabricate a fuel rail for top-feed injectors.

[qsiguy]

A blow off valve isn't really required unless you have a manual trans. Nice to have tho as it's easier on the intake components when you let off the gas from full boost and plus it just sounds cool

I'm not sure how you do boost control with a supercharger now that I think of it. I know it's done with various pulley sizes, is there any other boost control used on superchargers?

[Mettler]

Hmm, wouldn't a pressure relief valve after the supercharger be the go?

[qsiguy]

I suppose so. I guess a wastegate after the supercharger would do it but if the MAF was before the supercharger neither would be an option. Hmm.

Forget it...just get a turbo!

[hannibal]

I suppose so. I guess a wastegate after the supercharger would do it but if the MAF was before the supercharger neither would be an option. Hmm.

Forget it...just get a turbo!

No wastegate on a supercharger...

JT, didnt realize how big your turbo was til I googled it. I assume you fabbed your own /exhaust manifold and IC piping. Any pics of the manifold?

[Jeff Taylor]

The boost on a supercharger is "regulated" by its maximum shaft speed. Placing a smaller pulley on the blower will increase the boost pressure, because the compressor will spin faster. Most superchargers don't make full boost until very late engine speed.

hannibal - I re-fabbed the stock VH manifolds to point forward and collect into 2.5" v-band clamps. In the end, I should have built a set from scratch, because it would have taken less time. If I dig up any pictures I'll post them.

[valkyie]

JT, I thought about running a turbo set-up similar to what is in your picture. I saw another forum about a NA Z guy that did it also. He had the single turbo installed under the rear of the car and ran the pipes, oil, lines,etc. You know it would be easier just to install a turbo instead of playing around with the science of the SC.

I am a tank mechanic working in south korea for the army. So I have the mechanical knowledge just never really got into car modifications. I am just searching for a reliable and economical way to increase horsepower. Without the added boost to my 300zx NA then all other option of increasing WHP will not beeffective. Boost is the most effective way to increase ponies. So its back to the drawing board.

JT, when you find the time can you please make me a list of parts and material that I will need for this mod. I have a rough idea of what I will need but a list from your experience would really come in handy.

[Chrispy300]

The boost on a supercharger is "regulated" by its maximum shaft speed. Placing a smaller pulley on the blower will increase the boost pressure, because the compressor will spin faster. Most superchargers don't make full boost until very late engine speed.

Don't they have some sort of bypass valve for when the throttles is shut? You'd think that a PD blower into a closed throttle would only be bad news?

[valkyie]

I work in a army motorpool so I have alot of scrap aluminum laying around , three welder buddies , along with alot of other assets to help me with this project. Plus I am in south korea and labor here is DIRT CHEAP.

Once my supercharger book gets here I will study it and compare making a supercharger or installing a turbo.Basically I am going to use some turbo parts to make the SC. The pulley thats on the SC will be connected to a drive gear and that gear will mesh with smaller impeller gear turning the impeller at a higher speed then the engine giving me boost.

With the installation of the blow of valve between the intake manifold and the supercharger outlet set to 6 to 7 PSI regulated by the boost controller. I think I got it figure out from what I've been studying so far. If this sounds possible then let me know but if not let me know.

[SuperHatch]

Don't they have some sort of bypass valve for when the throttles is shut? You'd think that a PD blower into a closed throttle would only be bad news?

Centrifugal blowers are driven off the crankshaft and hold faily non-linear boost curves because the VE of the blower rarely matches the VE of the engine. You tend to get boost creep with these setups, and sometimes the bypass valve is used to regulate this, but not often. A centrifugal blower compresses the air BEFORE the throttle body much like a tubocharger, and as a result HAS a bypass/BOV to release the pressure when the throttle is closed, just as you've speculated.

A Positive Displacement blow is installed downstream of the throttle body, so there is no pressure on the atmospheric side of the throttle plate when it is closed. A roots type PD blower is not a compressor as much as it is a pump. The whole idea is that you set the blower to pump x times as much air as the engine intakes at a given RPM. If the engine flows 4.5L of air per cycle, then the blower might be driven to pump 6.75L of air per cycle resulting in 7.5psi ob boost pressure. The beauty of this is that the relationship remains failrly constant along a very broad RPM range resulting in near instantaneous off idle boost response and a broad flat torque curve. The downside is heat, and lots of it. That's why water to air IC's are placed between the blower and the manifold to cool the charge, and they're pretty much necessary at any boost pressure above 4 or 5 psi. A screw type PD supercharger does the same thing, but it also has an internal compression ration resulting in more boost as less RPM. Since the whipple can make the same pressure at lower RPM, it can either A: be underdriven resulting in less heat and more power than a similar size roots blower. Or B: Be undersized and overdriven resulting in the same heat as the roots blower, but a smaller package freeing up more space under the hood. Screw type blowers (Kenne Bell, Whipple) are very efficient compares to roots blowers. Still not as good as a turbo or centrifugal, but the broad torque is usually desireable as a tradeoff to it's downfalls.

PD blowers DO have bypass valves as well, but they recirculate between both sides of the blower when the throttle is closed so that air can bypass the blower to keep things cool. PD Sc's actually make more heat at idle and part throttle than when working to make boost pressure. Because of this their water to air cooling setups need to have a high volume to prevent heat soak.

Ok, I'm gunna shut up now...

[valkyie]

SH, Thank you for breaking it down for me. I'm really not to familiar with turbos, and supercharging. You really explained alot in good detail. The topic about running the intercooler I studied it before and some say you need and some you don't. Saying two turbo trans-am one running a cooler and one without had the same temperture at the intake. The study also stated unless you plan on not stop thats the only time a intercooler would be effective. A daily driver would not benefit from a cooler unless you do alot of highway driving. But I plan to run the cooler any because it looks cool. So I still just playing around with this for now until my supercharger book arrives. I figure the 6 to 7 PSI would not be to much on the engine and yes the will be 6 to 7 waiting at the throttle body with the blow of valve and boost controller regulating everything.

So today I found a old RX-7 turbo on ebay that I will use for my compressor and pre set the blow of 6 to 7 PSI if that can be done, I can wait for it to arrive so I can start to build my supercharger.

I plan to replace my fan with electric fan kit and mount a pulley in its place and use it to drive the supercharger. What do you think guys?

[SuperHatch]

I would not run a supercharger off of your water pump, the shaft loads would schread the bearings in the water pump in no time. I would run the belt directly to the crank.

[valkyie]

Thanks for the information. Well I will take a look and see exactly what I need to do to run it from the crank pulley. Don't want to damage my water pump. I think I will have to have a custom pulley made to run the belts plus some roller. I will figure it out step by step and post by post. I suppose I can have another pulley welded of the size I need onto the stock pulley. Well will see in how this all comes together.

[qsiguy]

valkyie, the way you are describing your BOV (blow off valve) it sounds like you think it will regulate boost pressure. That is not what it does. All the BOV is for is to open when you close the throttle so the pressure in the intake plumbing doesn't skyrocket and "dead head" the air flow from the turbo/supercharger. Biggest advantage when using a turbo is to keep the turbo from slowing down between shifts since you keep the air flow going. That wouldn't really make any difference with a belt driven supercharger since it won't slow down unless the engine slows down. I suppose it may put a load on the motor and drop RPMs faster than normal.

[valkyie]

Okay then well the question I have is if I run it wide open and the superchargers puts out lets set 10 PSI but I only want the entire system to run 6 to 7 PSI. What part reliefs, bleeds, or blows off thoughs few extra PSI from the system? Basically I don't want uncontrolled boost going into the engine intake. I want it to shut off at 6 to 7 PSI. When I build my supercharger I it will be designed to at best make 10 PSI. So I just have to figure out to control the boost. Any input anyone. Please keep in mind that this is a backyard build so some parts may get used in way it was not designed to do.

[qsiguy]

Change the pulley size. Larger pulley will reduce boost pressure.

You may be able to get a softer spring for your BOV so it will open at a set pressure level. The standard spring will handle a fairly high pressure. They don't open unless they have several PSI of pressure pushing on it as well as 15-20" of vacuum pulling on it at the same time.

[craigztoyz]

Now this is an informative discussion. I too want boost. And a Vortech may mount better then turbo, but how will the power be, torque curve, n boost levels per rms.

even with Nicks kicking in in the 2,000 range, and peaking in the 4,000 area, that is better then most. I always liked Vortech for SHO v6's because you had pull at 2K, but with the torque we have, I guess it may useable with turbo, as the boost wont kick in till you are moving, but what do you all think of running a vortech, water/air, and of course the tuning stuff Shane and Nick have gotten.

Just looking, have not had much discussion on this engine w/ a centrifical.

[valkyie]

That is correct a waste gate is designed to relief a over build up of exhaust gases. I will only need a blow off valve and boost controller. Can someone please tell me which type of intercooler would be best liquid or air?

[robb1971]

dont worry about a BOV on a supercharger, when you take your foot off the gas pedal the engine will slow down, when the engine slows the boost will decrease in proportion to the engine rpm.. boost is relative to the engine speed, its all in the pulley gearing as mentioned before.i wouldnt worry about an intercooler on a simple system with only low boost.. the vortech is ideal for what you are looking for, its like a turbo but is driven by a belt from your crank rather than exhaust gas, it looks like half a turbo with a pulley on the back end of it... its a dead easy concept and there is no need to mod the inlet manifolds. go to http://www.vortechsupercharger...RGERS there is even a section on BOV's if you need oneheres a pic from their web site, nice blower and an intercooler to boot
Modified by robb1971 at 3:38 AM 6/21/2008

[SuperHatch]

dont worry about a BOV on a supercharger, when you take your foot off the gas pedal the engine will slow down, when the engine slows the boost will decrease in proportion to the engine rpm...

Not true

With a centrifugal blower, at 7000RPM with a closed throttle, the SC will still be pumping enough air to generate Xpsi at wide open throttle, since it is a fixed drive it will still pump that volume of air when the throttle plate closes. That air will continue to be pumped regardless of throttle position as the engine speed decreases. That air has nowhere to go and slams against the throttle plate, reverses through the compressor, and/or gets forced through the IACV. ALL of which are bad. Low boost pressure setups can get away without a BOV, anything over 5 or 6 psi SHOULD have one, regardless of what Vortec or any other MFR tells you.

[craigztoyz]

Get away with, and a good idea, are two different things, yes it will work,but to be on the safe side, a BOV is important. Intercooler helps a lot too, as the compressed air is hot, but a lqd to air is expensive. Especially when bought through Vortech, but it helps a lot,

[hannibal]

Not true

With a centrifugal blower, at 7000RPM with a closed throttle, the SC will still be pumping enough air to generate Xpsi at wide open throttle, since it is a fixed drive it will still pump that volume of air when the throttle plate closes. That air will continue to be pumped regardless of throttle position as the engine speed decreases. That air has nowhere to go and slams against the throttle plate, reverses through the compressor, and/or gets forced through the IACV. ALL of which are bad. Low boost pressure setups can get away without a BOV, anything over 5 or 6 psi SHOULD have one, regardless of what Vortec or any other MFR tells you.

He's right...

As for water vs air intercooler, it depends on how youre using the car. If youre drag racing, the water to air IC may be better. You can use icy cold water and cool the incoming air BELOW ambient temps. For almost anything else, I'd go with an air to air IC...

[valkyie]

Qsiguy, I think I am going to the single turbo mounted in the rear, I got my supercharger book, its full of great info. Its just I don't have the time to for all the fabrication to the car and engine to install a custom supercharger. I am going to start putting together a list of parts I need. I was wondering if its possible if you can remember put together a list for me so that I have all my bases covered. When I do this mod I want to have everything in front of me. Also did you have to make a special mount or flange to mount the turbo in the rear?

[qsiguy]

I've posted so much info on my install you should be able to find most of what you need on these two posts.

zerothread?id=281662

http://turbo-infiniti.org/view...art=0

I'm still planning to go back through the car and do a bill of materials for the system, just not sure when I'll get around to it.